The Special Sensor Microwave Imager / Sounder (SSMIS) is a 24-channel, 21-frequency, linearly polarized passive microwave radiometer system. The instrument is flown on board the United States Air ForceDefense Meteorological Satellite Program (DMSP) F-16, F-17, F-18 and F-19 satellites, which were launched in October 2003, November 2006, October 2009, and April 2014, respectively.[1] It is the successor to the Special Sensor Microwave/Imager (SSM/I). The SSMIS on the F19 satellite stopped producing useful data in February 2016.[2]
The Department of Defense announced it would cut off access to SSMIS data useful for calculating depth of sea ice and location of hurricanes, as of July 31, 2025.[3]
In late July 2025, the Department of Defense announced it will keep the SSMIS data flowing until the sensor fails or the program formally ends in September 2026. [4]
Instrument characteristics
The scan geometry of the SSM/I(SSMIS have scan angle 143.2 grad)
The SSMIS sensor is a passive conically scanning microwave radiometer that combines and extends the current imaging and sounding capabilities of three previously separate DMSP microwave sensors: the SSM/T-1 temperature sounder, the SSMI/T- 2 moisture sounder, and the SSM/I. The SSMIS instrument measures microwave energy at 24 discrete frequencies from 19 to 183 GHz with a swath width of 1700 km.[5]
The first SSMIS was launched aboard the DMSP-16 satellite on 18 October 2003.
Due to a manufacturing mistake, the polarization for the channels at 50.3, 52.8, 53.6, 54.4 and 55.5 of the first unit of SSMIS (the one flying on DMSP-16) was reversed. Those five channels detect the vertical polarization rather than the Horizontal polarization detected by the successive units of SSMIS.[6]
^["Intercalibration between special Sensor Microwave Imager/Sounder and Special Sensor microwave Imager"; B. Yan and F. Weng; IEEE TGRS, 2008, 46, 984]
^Kunkee, David B.; Poe, Gene A.; Boucher, Donald J.; Swadley, Steven D.; Hong, Ye; Wessel, John E.; Uliana, Enzo A. (April 2008). "Design and Evaluation of the First Special Sensor Microwave Imager/Sounder". IEEE Transactions on Geoscience and Remote Sensing. 46 (4): 863–883. Bibcode:2008ITGRS..46..863K. doi:10.1109/TGRS.2008.917980. ISSN1558-0644. S2CID47668.
